The major scientific shortcoming of the Industrial Revolution that transformed the U.S. in the years after the Civil War was, and still is, pollution. One of the pioneers in the fight against pollution, especially in large cities, was the independent inventor Mary Walton.

As early as 1879, Walton developed a method for minimizing the environmental hazards of the smoke that up until then was pouring unchecked from factories all over the country. Walton's system (patent #221,880) deflected the emissions being produced into water tanks, where the pollutants were retained and then flushed into the city sewage system.

Some years later, Walton applied her ingenuity to a different kind of air pollution — noise. The elevated trains being installed throughout the larger cities of the U.S. in the 1880s were producing an intolerable amount of rattling and clanging: sociologists even blamed the noise for some urbanites' nervous breakdowns and neuroses! Walton, who lived in Manhattan, set out to solve the problem. She set up a model railroad track in her basement, and in time discovered an excellent sound-dampening apparatus. She cradled the rails in a box-like framework of wood, which was painted with tar, lined with cotton, and filled with sand. As the vibrations from the rails were absorbed by the surrounding materials, so was the sound.

After successful trials fitting her apparatus under the struts that supported real els, Walton received patent #327,422 (granted February 8, 1891). She sold the rights to New York City's Metropolitan Railroad, which thrived thanks to Walton's new, environment-friendly system. Walton herself was hailed as a hero — and as a feminist. As the Woman's Journal put it twenty years later: "The most noted machinists and inventors of the century had given their attention to the subject without being able to provide a solution, when, lo, a woman's brain did the work..."